Presently, it appears it may be due to the motherboard BIOS, not the card itself. If after examining additional motherboards, the results are the same, this means that the fix will be to ask the motherboard maker to provide a BIOS update with a fix. The fix is very simple. A register in the motherboard BIOS must be enabled which appears some may not have enabled it. Your motherboard must have Memory Type Range Register (MTRR) enabled. To check, you may do the following however this will require some technical knowledge:
First, download the file below:http://nvidia.s3.amazonaws.com/msd.zip
Unzip the files contents. You will need to run the utility in pure DOS (means you will need to create a DOS boot disk and boot off of the DOS boot disk). Add "device=himem.sys" in config.sys and load smartdrv.exe in autoexec.bat in the DOS boot disk or else the boot disk will take a long time to load. Type "msd.exe" to start the program. Then press TAB and left arrow key to "System Information" and press ENTER. Press PAGE DOWN key and you will see the Item 2. "Memory Information", in the bottom of this item you can see "Physical memory cache status". That's the MTRR setting for your system. If you see A0000~D0000 is uncacheable, that mean that the motherboard BIOS does not have MTRR enabled and is likely the cause of the slow POST issue.

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It is true that flashing your board incorrectly can damage the card but most problems that arise are from flashing your board with a video BIOS that was not meant for that particular model. For what it's worth, the version of the video BIOS which contains the workaround is 70.18.36.00.00. Any video BIOS later than this will also resolve this issue. I'll see if our channel sales team can work with our board partners to push the video BIOS update to resolve this issue.

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Linux. I've been suffering with slow boot since I bought the card months ago. It's fine from GRUB onwards - like others here it is not OS-related.
Motherboard is Asus V3-P5V900 with BIOS 1001 (i.e. the latest)
Card is Asus EN210 512M (GeForce 210) with VBIOS 70.18.2d.00.00

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We apologize for this slow POST issue you are having. Please contact us at OC_Support@asus.com so that we may get more detailed information about your VGA card in order to provide you with a VBIOS to resolve the issue. Please provide the part number and PCBA number of your VGA card which can be found on the barcode sticker on your VGA card. An example illustration of what the part number and PCBA will look like is below.
Anyone else also having this issue with an ASUS G210/GT220, please contact us at OC_Support@asus.com
-ASUS Support Team